Soul Echo enters the battlefield with X echo counters on it.
You don't lose the game for having 0 or less life.
At the beginning of your upkeep, sacrifice Soul Echo if there are no echo counters on it. Otherwise, target opponent may choose that for each 1 damage that would be dealt to you until your next upkeep, you remove an echo counter from Soul Echo instead.
10/4/2004 If you have more than one Soul Echo, the opponent chooses which ones will be replacing damage that turn (if any). And when damage happens, you decide which one of the ones the opponent selected that you want the damage to be replaced with, but the damage all goes to one of them.
10/4/2004 If this card runs out of counters before your next upkeep, the effect still replaces the damage and uselessly tries to remove counters from the now empty card.
10/4/2004 In a multi-player game, you choose a new opponent during each of your upkeeps.
10/4/2004 If you take damage between the start of the upkeep step and the time in which the upkeep trigger resolves, then Soul Echo will not affect that damage and you will be affected by the damage as normal.